(1) Field of the Invention
This invention relates to a novel electrical insulating oil composition. More particularly, the invention relates to an improved electrical insulating oil composition which exerts excellent deterioration resistance when it is brought into contact with substances made of lead or lead alloy.
(2) Description of the Prior Art
The electrical insulating oil is used for oil-filled or oil-impregnated electrical appliances and lead is used as a material for component parts of these electrical appliances.
For instance, in the case of oil-impregnated cables such as oil-filled cables and pipe-type oil-filled cables, they are commonly covered by lead or lead alloy material partly for preventing the impregnating electrical insulating oil from leaking. Further, included in the foregoing electrical appliances are oil-filled electrical capacitors and oil-filled transformers in which lead is used as a material for their component parts. For example, in the case of oil-filled capacitors, the oil supply tubes for filling oil into capacitors are made of lead and the lead tubes are pinched and cut off after the oil filling operation. As a result, certain portions of lead tubes remain within the capacitors, which tubes come into contact with the insulating oil. The component parts made of lead include such lead tubes.
When electric insulating oils are kept in contact with lead material, thermal deterioration and oxidation occur and, in some insulating oils, the degree of deterioration is too severe for practical use. This tendency can be observed in, for example, aromatic hydrocarbon insulating oils.